I'd say it's moreso that Sakaki is simply incapable of dreaming up a version of Osaka dopier than the real deal, so she acts in her dreams just like she would in the waking world.
5:24 Poor Chiyo-chan drowned... Also all the awkward pauses are just hilarious, I could Imagine one with Osaka appearing from nowhere, and do a Dave Miller by saying _"Why hello there, Old Sport"_